Abstract

This paper describes the development of a Unified Flow Solver (UFS) that automatically switches between and couples the continuum‐fluid‐dynamic and kinetic solvers needed for the continuum and kinetic regimes. A Direct Numerical Solver (DNS) of the Boltzmann Equation (BE) is used in regions of moderate and high local Knudsen number, while Kinetic schemes of gas dynamics are used elsewhere. The use of kinetic schemes instead of traditional continuum solvers facilitates automatic domain decomposition for coupling the BE and the continuum solvers. Solutions of several problems with small Knudsen number and in the continuum regime are presented. Criteria for switching between the kinetic and continuum solvers are formulated and tested. The efficiency and numerical stability of the UFS is attained by using similar computational techniques for the kinetic and continuum solvers, and by employing intelligent domain decomposition algorithms. Results obtained with the UFS for different problems are presented.